Effect of intercell spacing and operating conditions on the performance of prismatic lithium-ion batteries cooled by dielectric immersion Fluids:A numerical study

Abstract

Optimizing lithium-ion battery (LIB) packs for electric vehicles requires balancing the need to increase volumetric energy density with the necessity of effective thermal management to ensure performance and safety. Recently, the prismatic cell form-factor has enabled the cell-to-pack approach which increases the battery pack energy density. Additionally, dielectric fluid immersion cooling (DFIC) has emerged as a promising battery thermal management (BTM) technology. This article investigates the effectiveness of DFIC's in managing the thermal performance of modules composed of prismatic lithium-ion cells. Specifically, the influence of intercell spacing on cells' temperature, pressure drop across a module, and the volumetric energy density of the module was investigated. The electrochemical-thermal performance of cells at different mass flow rates of the coolant, coolant types, rates of discharge, and the resting time between a charge and a discharge was assessed. The single-particle electrochemical-thermal model has been used to model the performance of the batteries. The model results show that DFIC can maintain the maximum temperature and maximum temperature difference of a cell within 25–40 °C and 0–5 °C, respectively, even when the distance between cells is < 1.0 mm and at <10 g/min. By reducing the intercell spacing, the volumetric energy density increases by 8.33 %. At 0.25 mm with mineral oil coolant, the pumping energy accounts for only 0.00185 % of the module's total energy per cycle. Among the coolants studied, deionized water gave better overall performance. This study shows that DFIC is viable BTM technology for high-energy and high-power battery packs.